Ag(l)-C-H Activation Enables Near-Room-Temperature Direct α-Arylation of Benzo[b]thiophenes

摘要

The first example of near-room-temperature α-arylation of benzo[b ]thiophenes is reported. The discovery rests on the observation of a switch in α-/β-regioselectivity at different loadings of Pd_(2)(dba)_(3)·CHCl_(3) in the coupling between benzo[b ]thiophene and 4-iodotoluene. We show that this unprecedented regioselectivity switch is driven by a Ag(I)-mediated C–H activation at the α-C–H position, which becomes the dominant mode of reactivity at low concentrations of Pd. Competition experiments, kinetic studies, KIE, and D/H scrambling experiments have been carried out supporting this mechanism.